1. Field of the Invention
The present invention relates to a head suspension for a disk drive incorporated in an information processing apparatus such as a personal computer.
2. Description of the Related Art
A hard disk drive (HDD) records and reproduces information to and from rotating magnetic or magneto-optical disks. The HDD has a carriage turned around a spindle by a positioning motor.
An example of the carriage is disclosed in U.S. Pat. No. 4,167,765. The carriage of this disclosure includes carriage arms, a head suspension attached to a front end of each carriage arm, a head attached to the head suspension, and a slider attached to the head. When the disks are rotated at high speed, the sliders slightly float from the disks, and air bearings are formed between the disks and the sliders.
FIG. 13 shows an example of an HDD employing head suspensions according to a related art. The head suspension includes a load beam 101 made of, for example, a precision thin plate spring, a flexure 103 made of a very thin plate spring fixed to a front end of the load beam 101 by, for example, laser welding, and a base plate 105 fixed to a base part of the load beam 101 by, for example, laser welding. The base plate 105 is fixed to a contact face of a carriage arm 107.
FIG. 14 is an enlarged sectional view partly showing the base plate 105 attached to the carriage arm 107. The base plate 105 has a flange 109 and a boss 111. The flange 109 has a contact face 113 attached to the contact face 115 of the carriage arm 107. The boss 111 is inserted into a hole 117 of the carriage arm 107 and is plastically deformed therein, to attach the head suspension to the carriage arm 107. The plastic deformation of the boss 111 is carried out by, for example, passing a steel ball through a hole 119 of the boss 111. The steel ball expands the hole 119 and presses a peripheral face 121 of the boss 111 to the hole 117 of the carriage arm 107, thereby fixing the head suspension to the carriage arm 107.
Flatness of the flange 109 of the base plate 105 greatly influences contact between the carriage-arm contact face 115 and the base-plate contact face 113. It also influences fixation achieved by the plastic deformation of the boss 111.
The flange 109 must be thin to reduce the weight of the head suspension, and the boss 111 must have a sufficient thickness to secure strength. Pressing a plate material having a predetermined thickness into a base plate may provide the base plate with a sufficiently thin flange and a sufficiently thick boss.
Simply pressing a plate material into a base plate with a thin flange, however, leaves a fillet along a corner 123 between the flange 109 and the boss 111. The fillet interferes with a corner 125 of the carriage arm 107, to float or incline the flange 109 relative to the carriage-arm contact face 115. Then, even if the flange 109 is sufficiently thin and flat, the base plate 105 will improperly be fixed to the carriage arm 107 with the plastic deformation of the boss 111.
If the fixation of the base plate 105 to the carriage arm 107 is improper, the tightening torque of the base palate 105 relative to the carriage arm 107 will be insufficient and the insufficient tightening torque will destabilize the fitting of the head suspension to the carriage arm 107.